This invention relates to endodontic tools, and in particular, to tools used during and after an endodontic root canal preparation procedure, to more effectively clean the root canal system prior to obturation.
Following tooth maturation, the dental pulp is harbored within the structural elements of the tooth. Frequently, and for a variety of reasons, the pulp is irreversibly injured, resulting in inflammatory and infectious conditions which often adversely affect the tooth, its supporting structures, and the patient's health. Clinically, as an alternative to extraction, root canal treatment is performed and ideally directed towards the elimination of pulp, bacteria, if present, and their related irritants from the root canal system, followed by three-dimensionally filling of the root canal space with an inert, biocompatible, dimensionally stable, filling material, such as gutta percha. Ideally, the obturation procedures will fill not just the main canal, but the fins, webs, cul-de-sacs, lateral canals, and all the portals that communicate from the root canal system to the tooth's attachment apparatus.
Root canal procedures are common. Central to a successful endodontic treatment has been the use of chemical reagents during mechanical root canal shaping procedures (i.e., chemomechanical debridement) to completely clean all aspects of the root canal system. Chemicals and traditional methods used to enhance canal debridement and disinfection during cleaning and shaping procedures are limited by many factors that influence their potential to reach all aspects of the root canal system. The most popular chemicals currently used during canal preparation to actively assist in cleaning and disinfecting include bleach, hydrogen peroxide, and chelating agents, such as ethylenediaminetetracetic acid (EDTA) or citric acid. Often, a 6% solution of a clear, pale, greenish-yellow strongly alkaline bleach solution or sodium hypochlorite (NaOCl) and a 17% solution of EDTA are used.
During canal preparation, a solution of NaOCl is liberally irrigated into the root canal space where its solvent action facilitates the digestion and removal of pulp, bacteria, viruses, spores, endotoxins and other irritants generated by the microorganisms. This solution has the potential to circulate, penetrate and, hence, clean into all aspects of the root canal space. However, studies have shown that even the most thorough use of sodium hypochlorite does not remove all the material from the complex anatomy comprising a root canal. The walls of a root canal are comprised of dentin, which contains millions of dentinal tubules per square millimeter. Instruments used to negotiate and shape a canal cut dentin and produce debris which, in the presence of a solution, forms dentinal mud. In combination, dentinal mud, pulp tissue, and when present, bacteria, and their related irritants have been consistently visualized histologically after cleaning and shaping procedures in the dentinal tubules and various aspects of the root canal systems. Thus, after shaping procedures, the walls of the root canal are still covered with a film of debris, frequently described in the literature as a “smear layer.” This “smear layer” includes dentinal mud and potentially the organic debris, including the irritants noted above.
After shaping and cleaning procedures, the root canal has been traditionally filled with gutta percha and a root canal cement or sealer. However, if the smear layer or film is not adequately removed from the root canal, the smear layer can compromise the filling and sealing of the root canal system. If obturation is incomplete then the root canal space is predisposed to bacterial leakage and failure. Post-treatment failures attributable to leakage are common and require endodontic retreatment of the tooth or extraction. Thus, for a complete and thorough cleaning, this smear layer or film should be removed. Practitioners use a weak acid or surfactant, such as 17% EDTA, in an effort to remove the smear layer. Typically, the root canal is flushed with EDTA, or other similar reagents, to accomplish this. However, mere flushing of the canal with irrigating solutions does not effectively remove the smear layer from the canal. Some practitioners have used metal cutting files, metal non-cutting files, or metal cannuli (or needle) to activate the solution and enhance the performance of any given reagent. Traditionally, metal cutting and metal non-cutting files or cannula were manually activated. More recently, the metal cutting files, metal non-cutting files, and metal cannuli have been adapted to be connected to a handpiece to be vibrated sonically or ultrasonically.
When using vibratory energy, a sinusoidal shaped wave of piezoelectric energy passes along the length of any given metal object with a given frequency. This wave of modulation produces a characteristic pattern of nodes and antinodes along the length of the vibrated instrument. Because of the manner in which ultrasonic energy is transported, if the instrument contacts a surface, its back and forth movement will be limited and the desired ultrasonic energy will be reduced or dampened. Because virtually all root canals exhibit varying degrees of curvature along their lengths, it is impractical to think one skilled in the art could pass a vibrating file through the length of a root canal without touching the walls of the root canal. If an ultrasonically activated metal object touches a canal wall, then energy is significantly dampened and does not effectively reach the end of the file. Thus the distal end of the ultrasonically activated metal files (whether cutting or non-cutting) or metal cannuli will not vibrate sufficiently to induce hydrodynamic action in the reagent. Hence, the ultrasonic activation of metal instruments is limited in its ability to clean the root canal. Further, the use of ultrasonically driven metal instruments frequently leads to iatrogenic events, such as broken instruments, ledges in the wall of the root canal preparation, apical transportations or even perforations of the root canal. Hence, the use of ultrasonically activated metal devices contributes to undesirable iatrogenic events and dampening of the critical back and forth vibrational movement of any given device which is essential for cleaning. Ultrasonic or piezoelectric energy in curved canals frequently leads to the noted iatrogenic events, which can require corrective non-surgical retreatment, surgeries or extractions.
In my prior U.S. Pat. No. 6,179,617, which is incorporated herein by reference, I disclosed an endodontic brush for use in removing the smear layer. The brush is comprised of a handle, a shank and a brush section extending from the shank. The brush section includes a plurality of bristles extending from a twisted wire core. While this brush works acceptably, it still has many shortcomings which are due to the fact that the core and shank are disclosed to be made from wire. The two twisted wires which form the core and shank are each 0.2 mm in diameter, and hence, the core and shank have a combined diameter of at least 0.4 mm. While the wires are quite thin, even without bristles, the device, at times, has a diameter that is too large to reach the end of smaller diameter canals. From a technical standpoint, the wires cannot be made much thinner because the brush would then become predisposed to breakage during use. Even at the current diameter, the wire shank and core are too flexible. Because of its high flexibility, a dentist cannot effectively and purposely brush the sides of the root canal wall, and hence is limited in the ability to remove the smear layer from the root canal preparation. Additionally, because of the twisted wire core, the brush cannot be driven vibrationally. The twisted wire core prevents the transfer of vibrational energy to the bristles of the brush.
Since the brush may be too large for well-prepared, yet smaller diameter canals, I have encountered another limitation; namely that when the brush is placed into the canal, the reagent or solution in the canal is partially displaced by the brush. This is undesirable as it is through the use of various irrigants that dentists remove the pulp, bacteria when present and their related irritants, and the smear layer from the root canal system.
Additionally, prior sonically or ultrasonically driven endodontic tools require that the tool be threadedly attached to a driver by means of wrenches. This threaded connection makes it time consuming to change tools during a procedure. It would be desirable to make it easier to both attach and remove the tools from their drivers.